1. Field
Embodiments of the disclosure relate generally to the field of laser beam direction and more particularly to embodiments for a laser beam direction system incorporated with a window and achieving a required field of regard (FOR) for the laser weapon, or conversely maximizes the FOR for a given size window.
2. Background
Current airborne laser weapons utilize beam projectors either mounted in a turret arrangement on the nose of the aircraft fuselage as exemplified by the Airborne Ballistic Laser (ABL) operating on a modified Boeing 747-400F aircraft or which are deployed through a hole in the fuselage beneath the aircraft as employed in the Advance Tactical Laser (ATL) system currently integrated on C-130 aircraft.
The nose turret solution such as that adopted in the ABL occupies a location which is not feasible for many smaller aircraft for structural and aerodynamic reasons. The solution employing deployment through a fuselage hole is unacceptable beyond a certain Mach number and cannot be concealed readily.
Mounting of a conventional beam director behind a window causes the center of the beam to be displaced substantially as the beam director is positioned to orient a beam at a desired 3 dimensional angle. The offset of the center point of the emanating beam creates angulation of the beam which then slews across the window. The resulting location on the window of the beam center line and lateral extent of the beam therefore varies significantly. The window must consequently be enlarged to receive the entire beam width within the field of regard (FOR) for the beam created by the beam director. This would cause the size of the enclosing window to increase substantially. The size of the laser window is a significant issue because highly specialized and costly glasses must be used to achieve the low adsorption level required to avoid excessive adsorption in, and heating of, the window as well as excessive distortion of the laser beam. Extremely large pieces of such glasses are extremely costly or may require development of larger vacuum furnaces for fabrication and polishing. The window must conform to the complex curvature of the aircraft to minimize aero-optic effects on the laser beam. The complex curvature in the window is in itself a source of distortion of the laser beam and degradation in the performance of the laser system. All of these issues become more critical and complex where there are special surface treatment requirements for the aircraft such as stealth capability.
It is therefore desirable to provide a beam direction system for future airborne laser weapons which may be deployed on aircraft that require the beam use a projection system which is internal to the skin of the aircraft due to speed of operation of the aircraft, desired location of the beam projector, or stealth characteristics of the aircraft while minimizing the required window size to accommodate the necessary FOR for the beam.